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Effects of feeding generic ractopamine (Actogain) with or without the combination of monensin and tylosin phosphate on growth performance, carcass characteristics, and tenderness of finishing steers
The objective was to evaluate the effects of feeding generic ractopamine HCl (G-RAC; Actogain, Zoetis) with or without the combination of monensin and tylosin on growth performance, carcass characteristics, and tenderness of finishing steers. Ractopamine HCl (RAC) has previously been fed to finishing cattle under the trade name Optaflexx (Elanco Animal Health). Actogain is a feed ingredient containing RAC used to improve rate of weight gain and feed efficiency in cattle fed in confinement for slaughter the last 28 to 42 d on feed. Monensin (MON) and tylosin (TYL) are fed to beef cattle to prevent or control coccidiosis and reduce the incidence of liver abscesses when fed in combination with RAC. Steers (N=1230) were finished in six blocks of 3 pens each (1 pen per treatment) and were assigned to 1 of 3 different finishing diets: no G-RAC with MON and TYL (CON + MON/TYL), with G-RAC without MON and TYL (G-RAC – MON/TYL), or with G-RAC with MON and TYL (G-RAC + MON/TYL). Steers fed G-RAC – MON/TYL had 12 kg greater (P < 0.0001) final BW, 0.34 kg greater (P < 0.0001) ADG, 0.02 units greater (P < 0.0001) G:F, and 8 kg greater (P < 0.0001) HCW compared with steers fed CON + MON/TYL. Steers fed G-RAC + MON/TYL had 7 kg greater (P = 0.01) final BW, 0.24 kg greater (P < 0.001) ADG, 0.02 units greater (P < 0.0001) G:F, and 5 kg greater (P < 0.0001) HCW than steers fed CON + MON/TYL. Interestingly, steers fed G-RAC – MON/TYL had 5 kg greater (P < 0.01) final BW than steers fed G-RAC + MON/TYL; however steers fed G-RAC – MON/TYL had 1.06 and 1.00 kg greater (P < 0.0001) DMI compared with steers fed G-RAC + MON/TYL and CON + MON/TYL, respectively. No treatment effects (P ≥ 0.10) were observed for yield grade parameters (excluding HCW) and calculated yield grade. Marbling scores were 20.3 units (20% of one marbling score) less (P = 0.01) in steers fed G-RAC + MON/TYL compared with steers fed CON + MON/TYL. No treatment effects (P ≥ 0.06) were observed for Warner-Bratzler shear force after 14-d or 21-d of post-mortem aging. In conclusion, final BW, ADG, G:F, and HCW were increased in steers fed G-RAC with or without MON/TYL when compared with steers fed CON + MON/TYL, while other carcass characteristics were only minimally affected, similar to results from RAC-fed cattle.
Keywords: Actogain, beta-agonist, ractopamine, steer